African Dust Cooled 2006 Hurricane Season

Right-coasters and south-coasters can thank African dust for a quiet hurricane season in 2006. A little puff from just the right place in the Sahara cooled the pyrotechnics of storm formation. The Mother Jones piece "The 13th Tipping Point" (Nov/Dec 2006), explained just how Saharan dust is one of the critical global-warming tipping points keeping our world in balanceand likely to screw things up right royally if it falls out of balance.

Global warming is expected to shrink the Sahara by increasing rainfall along its southern border. A greener Sahara will emit less airborne desert dust to seed the Atlantic and feed its phytoplankton, to suppress hurricane formation, and to fertilize the CO2-eating trees of Amazonia. Hardly a neighborhood on earth will look the same if Africa tips.

Meteorological signs were unanimous in foretelling yet another hyperactive hurricane season, the eighth in 10 years. But the forecasts were far off the mark. The 2006 season was normal, and no hurricanes came anywhere near the United States or the Caribbean.

Now two climatologists are suggesting that dust blown across the Atlantic from the Sahara was pivotal in the busted forecasts. The dust seems to have suppressed storm activity over the southwestern North Atlantic and Caribbean by blocking some energizing sunlight, they say.

But, unremarked by forecasters, an unusually heavy surge of dust began blowing off North Africa and into the western Atlantic at the 1 June beginning of the official hurricane season. Two weeks later, the surface waters of the western Atlantic began to cool compared with temperatures in the previous season.

Climatologists William Lau of NASA's Goddard Space Flight Center in Greenbelt, Maryland, and Kyu-Myong Kim of the University of Maryland, Baltimore County, in Baltimore argue in the 27 February issue of Eos that the arrival of the thick dust and the subsequent cooling were no coincidence. The dust blocked some sunlight and cooled the surface, they say. That cooling went on to trigger a shift toward less favorable conditions for the formation and intensification of storms in the western Atlantic, they argue. As a result, no storm tracks crossed where nine had passed the previous season.